Methods—We analyzed data from the Jackson Heart Study (JHS), a population-based cohort study comprised exclusively of African-American adults (n=5,306). Analyses were restricted to 1,016 participants who completed ABPM at baseline in 2000-2004. Mean systolic BP (SBP) and diastolic BP (DBP) levels were calculated for daytime (10:00am-8:00pm), 24-hour (all available readings) and nighttime (midnight-6:00am) periods, separately. Daytime, 24-hour, and nighttime BP thresholds for ambulatory hypertension were identified using regression- and outcome-derived approaches. The composite of a cardiovascular disease (CVD) or all-cause mortality event was used in the outcome-derived approach. For this latter approach, BP thresholds were identified only for SBP as clinic DBP was not associated with the outcome. Analyses were stratified by antihypertensive medication use.